Don’t be fooled by the novel names like “hopscotch” loans or “spinversions”: rules announced Monday by the Treasury to curb corporate tax inversions are serious business.

Take the hopscotch loan for example. Such loans now let inverted companies avoid taxes on dividends by loaning to a foreign parent instead of the U.S. parent. Treasury’s rule would make such loans taxable as dividends in the U.S. That may impact Medtronic Inc.’s
/quotes/zigman/233680/delayed/quotes/zigman/233680/lastsaleMDTpurchase of Irish medical-device maker Covidien PLC, as Medtronic announced plans to lend some of its overseas cash to its new Irish parent.

Or consider the so-called spinversion – a partial inversion under which a U.S. company transfers some of its assets to a newly formed foreign corporation. That corporation is then spun off to public shareholders. New rules would treat the spun-off company as a domestic corporation. That move could hit pharmaceuticals company Mylan Inc.’s
/quotes/zigman/75764/delayed/quotes/zigman/75764/lastsaleMYLproposed takeover of Abbott Laboratories’
/quotes/zigman/216393/delayed/quotes/zigman/216393/lastsaleABT overseas generics business. Citi analyst Liav Abraham said in a note to clients the spinversion rule would “likely preclude Mylan’s ability to consummate its proposed transaction with Abbott’s ex-U.S. developed markets business.”

Another area of the new rules involves preventing companies from reducing their size before an inversion by paying out large dividends. That’s aimed at making it harder for U.S. entities to invert by beefing up the requirement that the former owners own less than 80% of the combined company.